As an abnormality detection system of a mobile robot such as a legged mobile robot, there is known the technology taught by Japanese Laid-open Patent Application No. 2001-150374. This system diagnoses itself for abnormalities and informs the user (operator) of the result of the diagnosis by voice via an audio output device and a communications interface, in a natural conversational manner.
A communications interface is generally susceptible to malfunctioning. Moreover, since the posture of a legged mobile robot, particularly a biped humanoid mobile robot, is unstable, the robot is apt to tip over when an abnormality arises within the system, and the communications interface is liable to be damaged as a result. When the communications interface fails, the probability of the self-diagnosis result being lost becomes high.
In addition, it is convenient to store in memory not only the fact of abnormality occurrence but also the time of the occurrence and/or the quantity of state such as the posture at that time, because this enables discrimination of the course of events leading up to the abnormality. However, the aforesaid prior art is not altogether satisfactory on these points.